Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
826 PM EST Tuesday Feb 9 2016
low pressure lifts well off the northeast coast tonight. An upper
level trough swings through the region later tonight. High pressure
slowly returns Wednesday through Friday. Low pressure lifts along
the southeast coast Friday and Friday night.
Near term /until 6 am Wednesday morning/...
rain showers tapering off south (mainly across NE nc) with the
loss of daytime heating and upper level shortwave energy.
Farther north across the Northern Neck and Maryland/Virginia Eastern Shore...still
seeing a combination of light rain or rain/snow showers. Best
shortwave energy present this evening is rounding the base of an
upper level low which is currently located over the eastern Great
Lakes. This feature is still on track to cross these same areas
closer to daybreak with light snow accumulations of less than
one half inch anticipated to occur on elevated and grassy sfcs
between 400 to 1000 am.
anomalous meridional flow prevails over the Continental U.S....highlighted by
a deep trough encompassing much of the eastern Continental U.S.. at the
surface...~991mb low pressure has centered well off the middle-Atlantic
coast with another area of low pressure over the eastern Great Lakes
region. A weak surface trough remains over the northestern local
area...providing better low level convergence for the Northern Neck and
Maryland Eastern Shore. NAM 285k Theta surfaces have handled the earlier
precipitation well...so continuing with that trend favors the
aforementioned areas of the Northern Neck and Eastern Shore...as well as southeast
Virginia/NE NC through the rest of the afternoon. Expect a wintry mix of
rain/snow over the Northern Neck and Maryland Eastern Shore...but expect all rain
southeast Virginia/NE NC as the warm layer is deeper and better mixed near the
coast. No snow accumulation is expected for the Maryland Eastern Shore through
6pm as surface temperatures remain in the low 40s with dewpoints in the
For the overnight...embedded shortwave/vorticity maximum reaches northern Virginia this
evening...developing a weak wave of low pressure along the surface
trough off the New Jersey coast. Expect precipitation to linger over the
Northern Neck/Eastern Shore through the evening hours. Low level critical
thicknesses begin to drop off sharply this evening as a colder/drier
air mass surges into the region. Expect a wintry mix to transition
to snow showers this evening for the Northern Neck/Maryland Eastern Shore...but surface
temperatures forecast to hover in the middle 30s. Dewpoints will fall into the
upper 20s resulting in wet bulbs in the low 30s. Do not expect the
best dynamics to arrive until late tonight...but not before the best
moisture pushes offshore. Minor snowfall accumulations are possible
on elevated and grassy surfaces...with amounts generally at or below half an
inch...mainly over the Maryland Eastern Shore. Will hold on to chance probability of precipitation for
snow showers through late tonight for the Maryland Eastern Shore as the vorticity maximum
pushes through. Sky remains generally partly cloudy to mostly cloudy
with westerly winds 10-15 miles per hour...preventing a sharp drop off in temperatures.
Lows in the middle/upper 20s.
Short term /6 am Wednesday morning through Friday/...
anomalous/deep upper trough prevails across the eastern Continental U.S. Wednesday as a
strong ridge persists along the West Coast. Surface low pressure lifts
off the New England coast through the day Wednesday as high pressure builds
over the Gulf of Mexico. Will maintain slight chance for snow
showers early Wednesday morning as the potent vorticity maximum pushes off the
Delaware-Maryland-Virginia. Otherwise...dry conditions prevail Wednesday as a cold/dry air
mass advects into the region. Steep lapse rates still present due to
the cold pool aloft so expect partly cloudy to mostly cloudy
conditions. Have stayed on the cold side of guidance...with highs
generally in the low/middle 40s. Westerly wind 10-15 miles per hour.
Trough axis aligns along the middle-Atlantic coast Wednesday night as
additional shortwave energy dives down the back side of the upper
trough. Expect mostly dry conditions as precipitable waters will be at or below 0.10
inches...but as colder air spills in...could see a few Bay enhanced
snow showers across mainly the Virginia Eastern Shore so will maintain 20-30
probability of precipitation there. Cold Wednesday night with lows in the upper teens Piedmont
to middle 20s along the coast. Dry/cold Thursday as the trough axis
pushes offshore...ushering in an even colder and drier Arctic air
mass. Highs generally in the low/middle 30s...or -1 to -1.5 Standard dev.
Sky averages sunny to mostly sunny.
High pressure settles over the region Thursday night and Friday as
additional energy digs over the Midwest into the Gulf states.
Associated area of low pressure prognosticated to develop off the southeast
coast Friday...with a slight chance for rain/snow across the southeast
late Friday. Slightly warmer...but still cold with highs in the
middle/upper 30s (-1 Standard dev).
Long term /Friday night through Tuesday/...
strong cold front crosses the region through the day on Saturday.
Behind the front...Arctic airmass is ushered into the mid-Atlantic.
Strong upper level dynamics may be enough to form a few snow shower
Sat morning. Wrap around moisture from weak area of low pressure
developing off the coast of the Carolinas may bring a slight chance
for -sn/-rasn across NE NC.
Strong cold air advection continues through the day on Sat with
925mb temperatures dropping 10c through the day. Thicknesses and
temperatures aloft continue dropping through the weekend as upper
trough swings across the area and surface high pressure builds
west...centering over the Great Lakes region. Expect high temperatures in
the middle/upper 30s. Coldest airmass of the season settles in Sat night
with lows dropping into the single digits and low teen sun
morning(lows over 20f below normal). Expect highs in middle/upper 20s on
sun with temperatures falling back into the teens Sun night.
Active weather patterns continues for the beginning of the work
week. With the surface high pressure moving off the coast...another
potent upper trough swings across the deep south. This will help
form an area of low pressure across the southeast U.S. That will move NE
late Monday into Tuesday. Uncertainty exists with this feature due to
slight model differences in timing of low development and track of
low. The models do suggest a multi-precipitation type event with an
onset of winter precipitation transitioning to a mix on Tuesday. Precipitation
prognosticated to move NE off the coast by Tuesday night
Aviation /01z Wednesday through Sunday/...
upper level low slowly moves east across the region through this forecast prd.
Ceilings gnrly VFR 5k-8k feet expect for scattered-broken MVFR cndtns (2-3k ft)
ivof sby. Radar trends have shown a decrease in echo coverage
since sunset largely due to the diurnal nature of the precipitation drng
the daylight hours. High res models show some rn/snow shower activity
scattered about the Northern Neck/Eastern Shore as well as southeastern coastal areas this
evening but little in the way of precipitation being rptd at any ob sites. This
data also shows a continued decrease in coverage next several hours
with only a low chance of any precipitation moving over a taf site. Thus...kept
all forecast dry through the night. Anthr weak impulse of energy prognosticated
to swing across the lower Maryland Eastern Shore around 12z. This may produce a
snow shower at sby but confidence not high enough to include in forecast.
West downsloping winds between 10-15 kts with g20 kts across Eastern Shore
areas Wednesday. This keeps lower levels dry with only scattered-broken cloudiness expeceted.
Outlook...VFR conditions prevail Wednesday night through Friday...as hi pressure
builds into the middle Atlantic region.
7-9ft seas in the Atlantic continue through this evening before
dropping to 5-7ft overnight.
Moderately strong pressure gradient and continual shots of cold air
aloft will help strengthen westerly flow over the waters tonight
through Thursday night. The result will be prolonged Small Craft Advisory conditions
across the ches Bay and NC/VA/MD coastal waters. Expect wind gusts
to average 25-30kt Wednesday morning through Thursday night over the coastal water
and 20-25kt over the Bay. Expect seas 3ft nearshore up to 5/6ft 20nm
off the coast with the offshore flow. Weak area of high pressure
settles over the middle-Atlantic by Friday allowing for a brief period of
non-Small Craft Advisory conditions.
Strong Arctic front prognosticated to cross the waters Sat night. Gale
conditions will be possible Sat night through Sun night as strong
cold air advection advection takes place and surface pressure gradient tightens
between departing low to the NE and building high from the west. A
period of freezing spray will also exist as temperatures will
quickly drop into the 20s and teens Sun morning with winds gusting
over 30kt. Winds diminish quickly Sun night as surface high centers
over the waters.
river Flood Warning remains in effect for the Nottoway at Sebrell.
The warning for Franklin was cancelled. See flsakq for details.
issued another round of coastal flood advisories and warnings for
the next high tide cycle tonight given the elevated water levels
due to the high anomalies. Warnings have been posted for the ches
Bay Side of the lower Maryland Eastern Shore...ches Bay Side of the Virginia Eastern
Shore and Northern Neck. Advisories have been posted farther south
across the middle and lower ches Bay except the mouth of the Bay.
Put oxb in an advisory for the high tide this evening given current
This all due to elevated water levels across the Bay as the recent
high seas has prevented water from exiting the Bay and tidal rivers.
In most areas the surge was 2 feet or greater.
Maryland...coastal Flood Advisory until 11 PM EST this evening for mdz024-
Coastal Flood Warning until 4 am EST Wednesday for mdz021>023.
Virginia...coastal Flood Advisory until 2 am EST Wednesday for vaz084-086-
Coastal Flood Warning until 1 am EST Wednesday for vaz099-100.
Coastal Flood Warning until 5 am EST Wednesday for vaz075>078-
Marine...Small Craft Advisory until 5 am EST Thursday for anz630>634-